This invention relates to an access control apparatus for use with a disc drive having a head provided for movement with respect to recording tracks formed on a disc to produce a reproduced signal.
Access control apparatus have been proposed for controlling the movement of the head in a direction radially of the disc to perform access from one recording track to a desired recording track. Accurate access to the desired recording track requires accurate counting of the number of recording tracks traversed by the head. For this reason, a counter is used for counting traverse detection pulses to accumulate a count correspoonding to the number of recording tracks traversed by the head. It is the current practice to produce the traverse detection pulses by processing the reproduced signal outputted from the head. A serious problem which would occur with this type of access control apparatus is that noise is combined with the traverse detection pulses, causing an error introduced into the accumulated count of the counter when the head traverse speed increases to an extent for the purpose of rapid access to the desired recording track.